Fabrication of Gradient Elements

Marchand, Erich W.

doi:10.1016/b978-0-12-470750-4.50015-3

Cited by 22 publications

(46 citation statements)

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“…22 The refraction analysis allows to discuss the temperature profile generated with a filament at a spatial resolution given by the cross section of the laser beam (several microns) and a time resolution given by the response time of the photodiode (several ns). The angular deflection is given analytically as an integral transformation of a general refractive index profile with cylindrical symmetry.…”

Section: Introductionmentioning

confidence: 99%

Laser schlieren deflectometry for temperature analysis of filamentary non-thermal atmospheric pressure plasma

Schäfer

Foest

Reuter

et al. 2012

Review of Scientific Instruments

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The heat convection generated by micro filaments of a self-organized non-thermal atmospheric pressure plasma jet in Ar is characterized by employing laser schlieren deflectometry (LSD). It is demonstrated as a proof of principle, that the spatial and temporal changes of the refractive index n in the optical beam path related to the neutral gas temperature of the plasma jet can be monitored and evaluated simultaneously. The refraction of a laser beam in a high gradient field of n(r) with cylindrical symmetry is given for a general real refraction index profile. However, the usually applied Abel approach represents an ill-posed problem and in particular for this plasma configuration. A simple analytical model is proposed in order to minimize the statistical error. Based on that, the temperature profile, specifically the absolute temperature in the filament core, the FWHM, and the frequencies of the collective filament dynamics are obtained for non-stationary conditions. For a gas temperature of 700 K inside the filament, the presented model predicts maximum deflection angles of the laser beam of 0.3 mrad which is in accordance to the experimental results obtained with LSD. Furthermore, the experimentally obtained FWHM of the temperature profile produced by the filament at the end of capillary is (1.5 ± 0.2) mm, which is about 10 times wider than the visual radius of the filament. The obtained maximum temperature in the effluent is (450 ± 30) K and is in consistence with results of other techniques. The study demonstrates that LSD represents a useful low-cost method for monitoring the spatiotemporal behaviour of microdischarges and allows to uncover their dynamic characteristics, e.g., the temperature profile even for challenging diagnostic conditions such as moving thin discharge filaments. The method is not restricted to the miniaturized and self-organized plasma studied here. Instead, it can be readily applied to other configurations that produce measurable gradients of refractive index by local gas heating and opens new diagnostics prospects particularly for microplasmas.

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Section: Introductionmentioning

confidence: 99%

Laser schlieren deflectometry for temperature analysis of filamentary non-thermal atmospheric pressure plasma

Schäfer

Foest

Reuter

et al. 2012

Review of Scientific Instruments

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“…The push for miniaturization renders ferromagnetic transition metals and their alloys to be materials of choice for the fabrication of spin-wave devices [5,6]. However, loss reduction, the shortening of the wavelength of studied spin waves, and the associated miniaturization of the implemented magnonic concepts and devices remain major challenges in both experimental research and technological development in magnonics [2,3].In this Rapid Communication, we explore an approach to meet these challenges that is based on the concept of gradedindex (or gradient-index) optics [7]. As applied to spin waves, this concept is based on the following basic ideas.…”

mentioning

confidence: 99%

“…In this Rapid Communication, we explore an approach to meet these challenges that is based on the concept of gradedindex (or gradient-index) optics [7]. As applied to spin waves, this concept is based on the following basic ideas.…”

mentioning

confidence: 99%

Towards graded-index magnonics: Steering spin waves in magnonic networks

et al. 2015

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Magnonics explores precessional excitations of ordered spins in magnetic materials-so-called spin wavesand their use as information and signal carriers within networks of magnonic waveguides. Here, we demonstrate that the nonuniformity of the internal magnetic field and magnetization inherent to magnetic structures creates a medium of graded refractive index for propagating magnetostatic waves and can be used to steer their propagation. The character of the nonuniformity can be tuned and potentially programmed using the applied magnetic field, which opens exciting prospects for the field of graded-index magnonics. Over the past decade, magnonics (the study of spin waves-precessional excitations of ordered spins in magnetic materials [1]) has emerged as one of the most rapidly growing research fields in magnetism [2,3]. Moreover, recent advances in the understanding of fundamental properties of spin waves in magnetic micro-and nanostructures have highlighted magnonics as a potential rival of or complement to semiconductor technology in the field of data communication and processing [4]. The push for miniaturization renders ferromagnetic transition metals and their alloys to be materials of choice for the fabrication of spin-wave devices [5,6]. However, loss reduction, the shortening of the wavelength of studied spin waves, and the associated miniaturization of the implemented magnonic concepts and devices remain major challenges in both experimental research and technological development in magnonics [2,3].In this Rapid Communication, we explore an approach to meet these challenges that is based on the concept of gradedindex (or gradient-index) optics [7]. As applied to spin waves, this concept is based on the following basic ideas. First, the propagation of spin waves is controlled using subwavelength, often continuously varying, magnetic nonuniformities [8,9]. This should minimize scaling of the device size with the magnonic wavelength, in contrast to, e.g., magnonic crystal based approaches [3], and thereby ease the associated patterning resolution requirements. Indeed, nonuniform effective magnetic field and magnetization configurations have been shown to confine [10,11] and channel [12][13][14][15] spin waves, to continuously modify their character [16][17][18], and to enable their coupling to essentially uniform free space microwaves [19,20]. Here, we go further by exploiting in addition the anisotropic dispersion inherent to spin waves dominated by the dynamic magneto-dipole field-so-called magnetostatic spin waves [1]. The symmetry axis of the anisotropic magnetostatic dispersion coincides with the direction of the magnetization [21][22][23]. This anisotropic dispersion leads to the formation of nondiffracting caustic spin-wave beams * Corresponding author: v.v.kruglyak@exeter.ac.uk [24][25][26][27][28][29][30] and to anomalous spin-wave reflection, refraction, and diffraction [31][32][33][34][35]. Here, we explore these ideas in networks of magnonic waveguides [6,8,[12][13][14][15][16][17][18][19][20]24,...

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“…where 0 n is the index-of-refraction at the center of the lens and a is the radius of the lens [20]. The fish-eye lens focuses rays emanating from a point on the lens surface to a conjugate point on the opposite side of the lens.…”

Section: The Flattened Maxwell Fish-eye Lensmentioning

confidence: 99%

“…where i indexes the general coordinate i q [20]. Equations (2) can be integrated to find the path of a ray through a medium with an arbitrary (but isotropic) index distribution, the position and direction of the ray serving as sufficient initial conditions.…”

Section: The Flattened Maxwell Fish-eye Lensmentioning

confidence: 99%

Enhancing imaging systems using transformation optics

et al. 2010

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Abstract:We apply the transformation optical technique to modify or improve conventional refractive and gradient index optical imaging devices. In particular, when it is known that a detector will terminate the paths of rays over some surface, more freedom is available in the transformation approach, since the wave behavior over a large portion of the domain becomes unimportant. For the analyzed configurations, quasi-conformal and conformal coordinate transformations can be used, leading to simplified constitutive parameter distributions that, in some cases, can be realized with isotropic index; index-only media can be low-loss and have broad bandwidth. We apply a coordinate transformation to flatten a Maxwell fisheye lens, forming a near-perfect relay lens; and also flatten the focal surface associated with a conventional refractive lens, such that the system exhibits an ultra-wide field-of-view with reduced aberration.

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Fabrication of Gradient Elements

Cited by 22 publications

References 0 publications

Laser schlieren deflectometry for temperature analysis of filamentary non-thermal atmospheric pressure plasma

Laser schlieren deflectometry for temperature analysis of filamentary non-thermal atmospheric pressure plasma

Towards graded-index magnonics: Steering spin waves in magnonic networks

Enhancing imaging systems using transformation optics

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